Energy efficiency: a non-criterion in industrial processes

摘要

A calculated comparison between gas and electrical aluminiummelting, from an energy efficiency as well as from a CO_2 emissionspoint of view, shows that there is a certain “imbroglio” concerningenergy efficiency as a strategy for industrial processingin climate change mitigation. Energy efficiency seems to be usedby many governments as a way of running with the hare andhunting with the hounds: pretending measures against climatechange, and safeguarding at the same time the possibility forindustrial growth. It is argued that “CO_2 emissions” or “life cycleanalysis” are more relevant assessment tools to evaluate the impacton climate change of an industrial process. Moreover, in industryit is production efficiency – defined as the ratio betweenproduction yield and production efforts – what really matters,and not energy efficiency as such. And also from a pure theoretical,thermodynamical, point of view it is exergy efficiency thatcan point out the possible economies in an industrial process.Consequently, for industrial processing it seems wise to makea split between the process itself and what is usually called “utilities”.By “utilities” secondary but essential resources are meantas there are: compressed air, speed drives, lighting, refrigeration,steam, hot water. For these “utilities”, standardized devicesand practices can be designed. This standardization makes itrewarding to have a primary concern for their energy efficiency.For the process itself, however, industrial experience learns thatthe first concern is to have the process running.Nevertheless, it can be forecasted that in the energy supplysystem of the future, energy efficiency will regain its importanceas an evaluation criterion, not in the context of impact onclimate change, but more as a performance parameter for theenergy management of an industrial process.